The value of morphometry, DNA flow cytometry and HER-2/neu oncoprotein expression for prediction of response to adjuvant chemotherapy in premenopausal lymph node positive breast cancer patients was evaluated in a group of CMF treated patients and controls with long-term follow-up. In the treated group, the Morphometric Prognostic Index (cutpoint 1.1) was the best prognosticator (p less than 0.0001, MC = 16.9), followed by the Mitotic Activity Index, the volume percentage epithelium and the number of positive nodes. For the controls, only the % HER-2/neu oncoprotein expression revealed significant differences (p less than 0.0001, MC = 16.3). When directly comparing treated patients and controls stratified for a certain parameter, no significant differences were obtained, although a trend towards improved survival in the treated group was present for some of the subgroups for several parameters. These preliminary results indicate that morphometric features and quantitative HER-2/neu oncoprotein expression may be important factors for identifying cases that will or will not respond to adjuvant chemotherapy.